Develop-19050-Frozen2/Unity-19050-05-BallPool/Assets/UnityUtils/Misc/DrawTrail.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class DrawTrail : MonoBehaviour {
    [Header("Trail")]
    public float framerate = 30.0f;
    public float duration = 30.0f;
    List<Vector3> trail_positions;
    float stamp;

    // Use this for initialization
    void Start () {
        trail_positions = new List<Vector3>();
        stamp = Time.time;
    }

    // Update is called once per frame
    void Update () {
        float dt = Time.time - stamp;
        if (dt > 1.0f / framerate)
        {
            stamp = Time.time;
            trail_positions.Add(transform.position);
            int max_count = (int)(duration * framerate);
            while (trail_positions.Count > max_count)
                trail_positions.RemoveAt(0);
        }
    }

    void OnDrawGizmos()
    {
        Color hex_color;
        // Trail
        if (trail_positions == null)
            return;

        if (ColorUtility.TryParseHtmlString("#F29F05", out hex_color))
        {
            Gizmos.color = hex_color;
            if (trail_positions.Count > 1)
            {
                for (int i = 1; i < trail_positions.Count; i++)
                {
                    float alpha = (float)i / trail_positions.Count;
                    Gizmos.color = new Color(hex_color.r, hex_color.g, hex_color.b, alpha);
                    Gizmos.DrawLine(trail_positions[i], trail_positions[i - 1]);
                }
            }
            Gizmos.DrawSphere(transform.position, 0.1f);
            Gizmos.color = Color.red;
            Gizmos.DrawLine(transform.position, transform.position + transform.right);
            Gizmos.color = Color.green;
            Gizmos.DrawLine(transform.position, transform.position + transform.up);
            Gizmos.color = Color.blue;
            Gizmos.DrawLine(transform.position, transform.position + transform.forward);
        }
    }
}